A novel and convenient procedure for synthesizing 3 ',5 '-dithiothymidine was described. In this procedure, DBU was used to form the intramolecular ring of 2,3 '-anhydrothymidine and then the thioacetic acid was used as solvent as well as the nucleophilic reagent to produce S-acetyl-3 '-thiothymidine. A very efficient deprotection step was applied to afford the target compound, which can avoid the oxidization of the thiol groups. And the key intermediate, 5 '-O-tosyl-2,3 '-anhydrothymidine, was found to have regioselectivity for different nucleophiles.